How mammalian spermatozoa develop their capacity for motility and fertilization in the epididymis remains one of the most challenging problems of reproductive physiology. The aim of the studies proposed here is to identify, test and devise conditions optimal for initiating spermatozoal "maturation". For this purpose, large numbers of testicular spermatozoa collected directly from the rete testis of conscious rams will be used to evaluate factors likely to imbue testicular spermatozoa with properties characteristic of ejaculated spermatozoa, including their morphological appearance, pattern of metabolism, composition, motility and fertilizing ability. The second part of the proposal is concerned with the control mechanisms of the three main functions of the testis: spermatogenesis, steroidogenesis and exocrine activity. Secretions of the two major fluid from compartments of the testis (rete testis fluid and testicular lymph) will be collected to study the effects of gonadotropic hormones on the distribution of androgens in the testis and the role of androgen-binding protein in androgen transport into the seminiferous tubules. The effects of the specific prolactin inhibitor 2-Br-alpha-ergocryptine on these functions of the testis will be studied by measuring the output of spermatozoa, fluid and androgens collected from the catheterized rete testis of conscious rams. Any successes in these studies may be applicable to reversible inhibition of sperm "maturation" or suppression of spermatogenesis in the adult human male desiring an effective means of fertility control.